Abstract
We probe the influence of branching on the configurational, packing, and density correlation function properties of polymer melts of linear and star polymers, with emphasis on molecular masses larger than the entanglement molecular mass of linear chains. In particular, we calculate the conformational properties of these polymers, such as the hydrodynamic radius , packing length p, pair correlation function , and polymer center of mass self-diffusion coefficient, D, with the use of coarse-grained molecular dynamics simulations. Our simulation results reproduce the phenomenology of simulated linear and branched polymers, and we attempt to understand our observations based on a combination of hydrodynamic and thermodynamic modeling. We introduce a model of “entanglement” phenomenon in high molecular mass polymers that assumes polymers can viewed in a coarse-grained sense as “soft” particles and, correspondingly, we model the emergence of heterogeneous dynamics in polymeric glass-forming liquids to occur in a fashion similar to glass-forming liquids in which the molecules have soft repulsive interactions. Based on this novel perspective of polymer melt dynamics, we propose a functional form for D that can describe our simulation results for both star and linear polymers, covering both the unentangled to entangled polymer melt regimes.
Highlights
Polymers play an important role in materials in everyday life, including film packaging, the molded parts of furniture, airplanes, and automobiles, as well as, diverse tools and devices for industry and the medical sciences
We propose a functional form for D based on Rh that can provide a description for unentangled and entangled polymer chains, as well as, for regular star polymers
Our findings suggest a tentative unifying framework of polymer melt dynamics that is agnostic about the role of topology on the nature of polymer diffusion
Summary
Polymers play an important role in materials in everyday life, including film packaging, the molded parts of furniture, airplanes, and automobiles, as well as, diverse tools and devices for industry and the medical sciences. When the length of the polymer chains is relatively long, the topological interactions between the polymer chains result in “entangled” structures that greatly restrict chain motion and augment the transmission of mechanical stresses within the material. It is not really clear at present to what. An additional source of concern about these models is their emphasis on the role of polymer topology in relation to the polymer motion within a background matrix of other fixed chains This type of phenomenological modeling leads to an increasing number of different mechanisms of polymer dynamics for each topology.
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